KVM: x86: Replace memset() "optimization" with normal per-field writes

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Explicitly zero select fields in the emulator's decode cache instead of
zeroing the fields via a gross memset() that spans six fields. gcc and
clang are both clever enough to batch the first five fields into a single
quadword MOV, i.e. memset() and individually zeroing generate identical
code.

Removing the wart also prepares KVM for FORTIFY_SOURCE performing
compile-time and run-time field bounds checking for memset().

No functional change intended.

Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/lkml/YR0jIEzEcUom/7rd@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>

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Sean Christopherson 2021-08-18 08:03:08 -07:00 • committed by Kees Cook

parent dfd42facf1

commit 73ab4a3509

2 changed files with 8 additions and 7 deletions

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9

arch/x86/kvm/emulate.c

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6

arch/x86/kvm/kvm_emulate.h

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